In the case of motor vehicles having an internal combustion engine, a so-called idle speed regulation is used. This idle speed regulation has the task of keeping the internal combustion engine at a so-called idle speed when a torque request from the driver is absent or too low, i.e., the accelerator pedal is not depressed. This idle speed regulation is performed by an idle speed regulator which is situated in a control unit of the vehicle engine. Furthermore, the control unit contains a drivability filter. This filter has a function of influencing the torque and filters the driver request for the purpose of avoiding Bonanza effects on the vehicle's drive shaft, in particular the delivery of a zero torque by the clutch.
During idling, the functions of the idle speed regulator and of the drivability filter result in a contradiction, since the idle speed regulator wants to build up the idle speed regulator torque rapidly. If this is done, Bonanza effects occur on the drive shaft of the vehicle, which results in reduction of driving comfort.
In order to achieve optimal filtering and determination of the zero torque level of the clutch, it would be optimal to add the entire idle speed regulator torque to the torque path upstream from the drivability filter. This has, however, the disadvantage of impairing the idle speed regulation, since the drivability filter causes a phase shift in the control loop.
A method and a device for operating a drive unit are known from DE 10 2007 013 253 A1. A first portion of the second setpoint value for the output variable predefined by a speed regulator represents a stationary portion of the second setpoint value for the output variable predefined by the speed regulator. Based on the consideration of the stationary portion in forming the first setpoint value, the stationary portion is also considered in the case of filtering the damping of the Bonanza effect. The function of damping the Bonanza effect in the case of an activated speed regulator may thus be performed more precisely. However, this method does not contribute to preventing the conflict described above in the case of dynamic idle speed regulator interventions.